Shale gas extraction from gas-rich shale areas deep underground is an emerging “unconventional” source of natural gas. Shale gas areas are often known as “resource plays,” meaning the geological chance of finding natural gas is high but the potential profit per successful well is usually low. This is in contrast to “exploration plays,” where the geological chance of finding natural gas is low but the potential profit per successful well is usually high. Shale deposits also typically have low porosity and permeability, so shale gas production in commercial quantities often requires both expensive hydro-fracturing of shale formations and the drilling of a large number of wells in a field. For these and other reasons, the production of shale gas is challenging both technically and commercially.